Dental primer adhesive system and optional hydrophobic resin

ABSTRACT

The present application relates to a polymerizable dental primer/adhesive system comprising a primer component having a relatively hydrophilic monomer component in an amount that renders the system relatively hydrophilic before polymerization of the system and capable of penetrating a prepared dental surface such as etched tooth dentin or enamel, and a multi-functional cross-linking agent in an amount that renders the system relatively hydrophobic after polymerization. A polymerizable hydrophobic monomer component is also included in the primer. The inclusion of said hydrophobic polymerizable monomer and said multi-functional cross-linking agent improves the long term stability or durability of the polymerized primer system to the dental restoration and to the tooth, dentin, enamel and other dental surfaces. An additional hydrophobic resin can also be employed with the primer adhesive system. The dental primer adhesive system exhibits greater stability and durability over time when compared to other dental adhesive systems.

The present application is a continuation of U.S. patent applicationSer. No. 12/021,808, filed Jan. 29, 2008, which claims priority to U.S.Provisional Patent Application No. 60/898,014 filed Jan. 29, 2007, allof which are incorporated by reference herein.

DESCRIPTION OF RELATED TECHNOLOGY

Advances in dental restorative techniques include the use of variousmaterials such as composite resins to effect tooth filling or otherrestorative processes. Other advances include the use of dentalcomponents such as thin wire braces and other types of dental componentsmade of metal, ceramics, resins or other bio-compatible substances.Depending on the clinical application, such restoratives and componentsmay be applied directly to the tooth dentin and/or enamel, or may beapplied to other bio-compatible substrates such as metals, ceramics,resins, amalgams, or other restorative materials which may already existin the patient and/or are to be added as part of the clinical treatment.

Common to the foregoing materials and techniques is the need for bondingsystems to enhance the bonding of the restorative or other dentalcomponent to the chosen dental substrate. Ideally, such enhancementwould provide bond strengths which approach the strength of theunderlying substrates. In addition, ideal bonding systems would also besimple for the dental professional to use in a manner which requires aminimum of time for the patient in the chair.

Several bonding systems and techniques have been reported in theliterature which have achieved some, but not all of the above-statedgoals. Such bonding systems can be divided into three generalcategories, multiple-component primer systems, two component primersystems, and single-component primer systems.

A. Multiple Component Bonding Systems

A general discussion of multiple-component bonding systems and theirpredecessors is set out in Suh, “All-Bond—Fourth Generation DentinBonding System,” J. Esthetic Dentistry, Vol. 3, No. 4, pp. 139-147(July-August, 1991) and in Bowen U.S. Pat. No. 5,270,351 at Col. 1,lines 29-Col. 2, line 36 and Col. 2, lines 54-64, the disclosures ofwhich are hereby incorporated by reference. Briefly summarized, theearly generation bonding systems generally disclosed at Col. 1 and 2 ofthe '351 patent began with simple pretreatment of the dental substratewith mordants and/or acidic solutions before application of the dentalrestorative or component. Such systems, while simple to use, did notprovide high bond strengths on substrates such as tooth dentin.

Those low bond strengths led to the development of themultiple-component bonding systems discussed at Col. 2 of the '351patent and discussed in detail in the J. Esthetic Dentistry article atpp. 139-147. Such systems generally employed the older generationsystem's first step of pretreatment of tooth dentin or enamel withacidic solutions to decalcify and remove dentin smear layer and to etchtooth enamel (a technique often referred to as “total etch” process, asboth dentin and enamel may be etched using a low pH solution). Themulti-component systems then employed two or more separate “primer” or“adhesive enhancing” compounds to further enhance bonding between thesubstrate and the dental restorative. However, the primers in suchsystems must either (1) be applied separately and sequentially to thedental substrate, or (2) must be mixed together by the dentalprofessional in the office immediately before use on the patient toprevent premature polymerization of the components.

The first type of such multiple-component primer systems is exemplifiedin Bowen U.S. Pat. Nos. 4,514,527, 4,551,550, 4,558,756 and 4,659,751,and U.S. Pat. No. 4,964,911 Ivson et al., (and related Ibsen et al. U.S.patents re 34937) discussed at Col. 2 of the '351 patent. Those earlierpatents disclose, inter alia, two or three component primer systemsemploying the separate steps of treating the dental substrate with (1)an acidic acid solution of inorganic acids, polycarboxylic acids andmetal salts of such acids capable of changing valence states, (2)applying a first primer compound comprising N-arylglycine andderivatives such as NTG-GMA (the adduct of N(p-tolyl)glycine andglycidyl methacrylate), NPG (N-phenylglycine), and other amino acids andmetal salts thereof to the substrate, followed by (3) applying a secondpolymerizable adhesive bonding monomer to the substrate comprising PMDM,BDTA-HEMA, 4-META, or other polymerizable acidic monomers disclosedtherein and having groups or moieties that do not interfere withpolymerization. Although some of those systems report achieving moderatebond strengths for bonding to substrates such as tooth dentin, fromabout 1600 to about 2500 p.s.i (11-17 Mega Pascals (1 MPa=145 p.s.i.)),such multi-component/multi-step methods are necessarily complicated forthe dental professional and time-consuming for the patient.

B. Two-Component Primer Systems

As an alternative to multiple-component primer systems, Bowen andothers, including applicant's assignee, Bisco, Inc., have reporteddevelopment of two-component primer systems. See e.g., Bowen U.S. Pat.Nos. 5,320,886 and 5,270,351, Suh et al. article cited above and U.S.Pat. No. 5,348,988 and Bunker U.S. Pat. No. 4,544,467. Such systemsinvolve steps whereby the dental professional admixes the two primercomponents immediately prior to application of the mixture to the dentalsubstrate. Immediate application is required in such systems because theprimer composition begins to polymerize upon mixing due to the chemicalnature of the primer molecules, at least one of which containsethylenically unsaturated (vinyl) groups whose polymerization isinitiated by the tertiary amine group present on the other primercomponent of the system. The two-component primer bonding systemstypically require an acid-etch step to provide a secure bond between thedentin and/or enamel and the primer, resulting in the so-called “hybridlayer” wherein the dentin/enamel and primer interface with one another.

A different type of a two-component primer bonding system is disclosedin Waknine U.S. Pat. No. 5,276,068. That two-component system comprisesa polymerization initiator and a polymerizable compound which arepackaged separately. The first step in that system requires applicationof polymerization initiator alone to the dental substrate. In a secondstep, the polymerizable compound is applied to the substrate.Polymerization begins when the polymerizable compound comes into contactwith the initiator on the substrate surface.

Some of the aforesaid multiple-component primer systems were reported asproviding only moderate dentin adhesive bonding strengths. For example,the data included in the Bowen '351 and '886 patents show dentinadhesive bond strengths of from about 10 to about 15 MPa. Moreover, thehigher bond strengths reported in the '351 patent were achieved onlyafter an additional step and component, comprising applying an unfilledadhesive resin monomer to the primed substrate before application of thedental restorative composite material, was added to the restorativeprocess. (See '351 patent, Example 1.) The Waknine '068 patent alsoreports relatively low bond strengths in the 10 MPa range and also usedan additional step of application of a commercial bonding resin (seeExamples 22-23.) Bunker et al. reported slightly lower dentin shear bondstrengths of between about 5 MPa and 8 MPa (49.3 to 86.5 kg/cm²).

Surprisingly, Suh et al.'s two-component primer system utilizingpolymerizable acidic monomer biphenyl dimethacrylate (BPDM) achievedbond strengths of between 22 and 27 MPa for dentin bonding, whichapproaches or equals the point of cohesive failure of tooth dentin. Highbond strengths of around 23-26 MPa were also achieved with that twocomponent priming system for bonding to tooth enamel. (See, e.g., J.Esthetic Dentistry article, Hydrophilic Primer Adhesive System andOptional Hydrophobic Resin).

C. Single Component Primer Systems

Additionally, there have been reported certain “one-component” or“single step” dental bonding systems. See, for example, Blackwell et at.U.S. Pat. Nos. 4,657,941 and 4,816,495 and Huang et at. U.S. Pat. No.4,966,934 all of which are assigned to Dentsply Research and DevelopmentCorporation (hereinafter also collectively referred to as the Dentsplypatents) and Bunker U.S. Pat. No. 5,304,585.

The Bunker et al. system is reported as involving polymerizablephosphoric acid ester adhesives. Such compositions are generallydisclosed therein as capable of being packaged with polymerizationinitiators in the presence of polymerization inhibitors and othercompounds in one package. (See '585 patent, col. 10, line 31 to col. 11,line 8.) However, such one-component packaging is not exemplified in the'585 patent. Instead, a two-component was tested in Example 1 of thatpatent, involving admixing of the polymerization initiator sodiumbenzenesulfinate first component with the phosphorous ester monomersecond component immediately before application to the tooth substrate.Bunker et al. also reported relatively low bond strength to dentin ofaround 9 MPa. (See '585 patent, col. 12, lines 16-42.)

The Dentsply patents also disclose alleged one-component dentin andenamel bonding primer and adhesive systems. Such systems are reported asbased inter alia on phosphorous-containing adhesion promoter compounds.However, the phosphorous-based bonding systems disclosed in the examplesof '941 and '495 patents all gave relatively low bond strengths of 8.39MPa or less.

The dipentaerythritol pentaacrylate phosphoric acid ester-based (PENTA)bonding systems disclosed in the '934 patent were reported as generatinghigher dentin bond strengths in the range of 10-27 MPa. (See '934 patentExample 10.) However, also reported therein is data showing that thehigher reported bond strength systems were not stable over time, withthe 27 MPa strength system reported as decreasing to around 10 MPa orless after 1-2 weeks storage of the system at elevated temperatures.(See '934 patent, Table VIII.) Moreover, the higher bond strengthsreported in the '934 patent were in actuality two-component systems inwhich a second commercial, unfilled adhesive bonding resin component wasused after application of the phosphorous primer composition. (SeeExample 4 and Example 10 at Col. 17, line 60-Col. 18, line 53 and TablesIX and X.) The “most promising” PENTA-based bonding systems disclosed inthe '934 patent were further tested with that additional second adhesivecomponent and step which were reported to provide bonding strengths fromabout 17 to 20 MPa. (See Table X.) In all three Dentsply patents, theprimer curing system was reported as light-curing done after eitherapplication of the composite resin material and/or after application ofa separate adhesive resin. (See Example 4 of '941,495 and 934 patents.)

U.S. Pat. No. 4,525,256 discloses certain one componentphotopolymerizable resins containing certain tertiary amineaccelerators. However, such compositions are composite (filled) resins,and not dental primer or adhesive compositions. (See '256 patent,Examples 1-3.)

U.S. Pat. No. 5,295,824 discloses inter alia plastic orthodontic deviceswith a “shelf-stable” monomeric adhesive layer pre-coated and “solvated”into the plastic device. The bond strengths reported therein are about10-20 kg, which if meant to be kg/cm², translate to rather low levels ofaround 2-4 MPa.

PCT application publication No. WO/93/02630 discloses an adhesive-coatedorthodontic bracket. The bracket's adhesive layer comprises ethoxylateddiglycidyimethacrylate of Bisphenol A (Bis-GMA), Bis-GMA and/or othermonomers and photo-initiator catalysts and inhibitors. The bond strengthof such pre-coated brackets were reported to be in the range of 54-104kg/cm² (about 5-10 MPa).

D. Bond Strength and Etching Systems

In general, the three step process of etching/rinsing, applying aprimer(s), followed by an adhesive, and thereafter followed by arestorative resin has been reported in the literature as the “goldstandard” of achieving high bond stability and durability in a dentalrestoration bonded to dentin. De Munck et al., J. Dent. Res.84(2):118-124 (2005). However, three step process restorations arereported to be more labor intensive and technique sensitive, and thetechnique used can significantly influence the resultant bond strength.Id. Nonetheless, reported laboratory results show that three step etchand rinse systems provide in an average initial dentin microtensile bondstrength (μTBS) that is higher than that reported for acid etched andself-etched two-step adhesive systems. Id. Self-etched single componentsystems were reported to have the lowest initial microtensile bondstrengths. Id.

Commercially available single-component self-etching bonding systems arereported as being promoted for use primarily for ease of use and lowtechnique sensitivity, as well as good performance in class V clinicaltrials. Inoue et al.; J. Dent. Res 84(12):1160-1164 (2005). However,aside from the relatively low initial dentin and enamel bond strength,self-etch single-component systems employing functional acidicmethacrylate monomers with water that are stored together in a singlebottle have been reported to degrade via hydrolysis during storage.Nishiyama et al., J. Dent. Res. 85(5):422-426 (2006) (describing suchsimplified self-etch adhesives as having “poor shelf lives”). Further,such degradation has been reported to occur as early as one month fromthe date of manufacture when kept at 25° C. Id.

E. Bond Strength and Hydrophilicity

Apart from initial bond strength, recent studies have tested the bondstrength of various resins when exposed to conditions approximatingthose experienced in vivo over time. In particular, it has been reportedthat resins formed from relatively hydrophilic monomers results in asubstantially weaker bond strength after cured, largely due tohydrolysis, elution, and the formation of water trees within the hybridlayer. Yiu CK, Biomaterials (25):5789-5796 (2004). Those, studies reportthat the greatest absorption of water in hydrophilic compounds occurswithin the first day of exposure to water. Id. In addition, hydrophilicacidic resins were reported to show the greatest decrease in bondingstrength within the first month of exposure to water. Id. Recent studiessuggest that some commercial single-step dental bonding systems arehydrophilic and have their greatest water-absorption during the firstfew weeks of storage in water. Malacarne J, Dent. Mater. (22): 973-980(2006).

Therefore, an improved two or three-step restoration system showinghigher initial bond strength and improved bond stability and durabilityover time would be appreciated by those in the art.

DESCRIPTION

According to the present invention, an improved dental adhesive andrestoration system is disclosed. In particular, it has been found thatuse of a primer A and B system having a polymerizable component thatcomprises a monomer component relatively hydrophilic beforepolymerization of the system and is relatively hydrophobic afterpolymerization of the system, when used alone or in association with anadditional hydrophobic resin, creates strong initial bonding withimproved long term stability and durability.

More specifically, it has been found that inclusion in one of the primercomponents of a relatively high cross-linking agent such as amultifunctional (meth)acrylate monomer having at least four functionalgroups improves the stability of the system relative to degradation dueto exposure of the system to water. In addition, the inclusion in aprimer component of a relatively hydrophobic monomer(s) improves thestability of the system.

In particular, it has been found that when a primer/adhesive systemcomprising a first primer component A comprising ethanol and an aminoacid salt derivative N(p-tolyl)glycine glycidyl methacrylate magnesiumsalt (Mg NTG-GMA) and a second primer component B comprisingpolymerizable acidic monomer BPDM (biphenyl dimethacrylate),dipentaerythritol pentaacrylate (“DPEPA”), relatively hydrophobic resinBisGMA or ethoxylated BisGMA, and initially hydrophilic monomer2-hydroxyethyl-methacrylate (HEMA), and camphorquinone (“CQ”) creates aneffective hybridization layer when mixed and applied to a tooth surfaceprepared with an acid etch (of approximately 20%-50% phosphoric acid)and rinsed with water prior to application of the primer mix.

In one embodiment, a hydrophobic dentin/enamel resin is applied over atooth surface prepared and primed with the primer/adhesive systemdescribed above. For example, a hydrophobic resin may comprise BisGMA,urethane dimethacrylate (“UDMA”), triethyleneglycol dimethacrylate(“Tri-EDMA”), ethyl 4-dimethylaminobenzoate (“EDMAB”), CQ, and4-methoxyphenol (“MEHQ”).

It has also been found that removal of monomers such as HEMA from theresin, while including such a hydrophilic monomer in the primer, resultsin a high initial bond strength with improved long term bond strength.

Example I

For example, according to one exemplary embodiment, a primer/adhesivesystem comprises a part A comprising from approximately 90-99% (byweight) ethanol and approximately 1%-10% (by weight) of an amino acid orits salt derivative such as Mg NTG-GMA; and a part B comprising apolymerizable acidic monomer such as BPDM at about 5%-30% (by weight),about 10%-40% HEMA (by weight), about 5%-15% DPEPA (by weight), about20%-60% (by weight) of relatively hydrophobic resin BisGMA orethoxylated BisGMA, and about 0.1%-1% CQ (by weight). According to oneexemplary embodiment, Part B may comprise a polymerizable acidic monomersuch as BPDM in an amount about 10% (by weight), about 38% HEMA (byweight), about 10% DPEPA (by weight), about 41% (by weight) ofrelatively hydrophobic resin BisGMA or ethoxylated BisGMA, about 0.5% CQ(by weight), and about 0.5% EDMAB (by weight). Additionally, ahydrophobic resin may comprise approximately 20-30% BisGMA (by weight),approximately 20-30% UDMA (by weight), approximately 30-47.77% Tri-EDMA(by weight), approximately 1.00-1.75% EDMAB (by weight), approximately0.30-0.45% camphorquinone (by weight), and approximately less than 0.1%MEHQ (by weight). As shown below in Table 1, the initial bond strengthto dentin when a first acid etch/rinse is applied is approximately 60MPa, with no statistically significant reduction in strength after 24hours. In this instance, microtensile bond strength was tested accordingto the methods generally described in Sano et al., Dent Mater (10):236-240 (1994). Optionally, the resin may contain a filler or radiopaquefiller such as Ytterbium fluoride (YbF3) that may comprise approximately10%-50% by weight of the resin composition.

When the primer is used along with the HEMA free resin, the bondstrength after 24 hours did not decrease.

TABLE 1 MICROTENSILE BOND STRENGTH TO DENTIN Example I Primer Example 1Primer (A + B Only) (A + B) & Resin) Standard Standard DeviationDeviation Strength (“SD”) Strength (“SD”) Same Day 37° C. 60.0 MPa 14.7MPa 55.3 MPa  9.8 MPa in H₂0 LC 24 Hours at 37° C. 60.0 MPa 13.2 MPa62.4 MPa 11.1 MPa in H₂0 LC Self Cure 58.2 MPa  9.3 MPa NA NA 24 Hoursat 37° C. in H₂0

Further, according to one embodiment of the present application, longterm testing over 24 months, as shown in Table 2 below, shows that theabove-described primer composition alone continues to retainmicrotensile bond strength (“μ-TBS”) over the entire period when exposedto water in an accelerated aging test when used alone or with a filledDentin Enamel (“D/E”) resin.

TABLE 2 ACCELERATED AGING TEST OF BOND TO DENTIN ULTRADENT SHEAR BONDTEST Prior Art Primer Example 1 Primer Example 1 Primer with D/E Resin(A + B) Only (A + B) & Filled D/E Resin Standard Standard Standard LightCure Strength Deviation Strength Deviation Strength Deviation Initial 2433.8 MPa 5.9 MPa 35.1 MPa 4.6 MPa 41.6 MPa 6.6 MPa Hrs at 37° C. in H₂024 Months 23.5 MPa 7.0 MPa 34.4 MPa 4.6 MPa 47.9 MPa 6.8 MPa at 37° C.in H₂0

In addition, the sample was tested according to the use of the Ultradentshear bond test by using an Ultradent jig as described generally in thearticle: Pashley et al., Dent. Mater. 11: 117-125 (1995). Furthertesting in water for 24 months and 45 months at 37° C. further supportsthe findings set forth in Table 2 above. As summarized below in Table 3,aging testing in water showed that shear bond strength did notappreciably reduce over 24 months in the novel primer/adhesive systemdescribed as Example 1. Further, only slight reduction in shear strengthwas shown in the water aging test at 45 months.

Aging testing of the primer disclosed above when further bonded with afilled D/E resin as discussed above further showed surprising resultscompared to the teachings of Yiu et al. Specifically, when tested inwater for 24 months and 45 months at 37° C., the bonding strengths ofthe primer/adhesive system to dentin when used along with a hydrophilicresin such as that described above show that the system remained stable,exhibiting resistance to water-induced degradation.

TABLE 3 LONG TERM AGING TEST IN H₂O - SHEAR BOND STRENGTH OF BOND TODENTIN AS SUBSTRATE ULTRADENT SHEAR BOND TEST (MPa) Example 1 PrimerExample 1 Primer (A + B) & (A + B) Only Filled D/E Resin StandardStandard Light Cured Strength Deviation Strength Deviation Initial at37° C. in 35.1 4.6 41.6 6.6 H₂0 LC 24 Months at 37° C. 34.4 4.6 47.9 6.8in H₂0 LC 45 Months at 37° C. 29.6 6.4 45.9 6.1 in H₂0 LC

Table 4 shows the bond strength of adhesives commercially available whencompared to a primer/adhesive system according to the present invention.Each of the commercially available bonding systems were compared withthe primer/adhesive system as disclosed above, as well as theprimer/adhesive system and an additional hydrophobic resin comprising29.5% BisGMA (wt), about 29.5% UDMA (wt), about 39% TriEDMA (wt), about1.435% EDMAB (wt), and about 0.369% CQ (wt), and 0.025% MEHQ, each ofwhich were applied using the total etch technique. As will beappreciated, the primer/adhesive system according to the presentinvention, when used alone or in combination with a hydrophobic resin,resulted in an initial bond that is very high, coupled with long termbond stability and durability that is better than any other adhesivesystem tested.

TABLE 4 LONG TERM AGING TEST OF ADHESIVES μ-TBS - EXPOSED SPECIMENS WITHDENTIN AS A SUBSTRATE (ALL RESULTS IN MPa) Total Etch Adhesives 24 HR(SD) 6 Weeks (SD) 24 Weeks (SD) Example 1 Primer 57.7 (15.8) 65.7 (11.8)65.2 (15.6) (A + B) Only at 37° C. in H₂0 LC Example 1 Primer 62.8(4.9)  61.4 (13.6) 61.0 (10.1) (A + B)+ Filled Hydrophobic Resin at 37°C. in H₂0 LC Scotchbond MP 49.1 (14.0) 64.0 (11.7) 44.1 (15.3) at 37° C.in H₂0 LC One-Step 65.2 (11.3) 69.5 (14.2) 58.0 (13.4) at 37° C. in H₂0LC Singlebond 75.1 (12.4) 66.6 (12.6) 54.0 (23.0) at 37° C. in H₂0 LC

Further, according to at least one embodiment of the presentapplication, long term testing over 6 months, as shown in Table 5 below,shows that one exemplary embodiment of the adhesive system, when bondedto dentin continues to retain microtensile bond strength (“μ-TBS”) overthe entire period when exposed to water at 37° C. in an aging test.According to at least one embodiment, a dental adhesive systemcomprising a Part A primer component comprising 2% Mg-NTG-GMA (wt) and98% absolute ethanol (wt), and a relatively hydrophilic Part B primercomponent comprising 10% BPDM (wt), about 38.75% HEMA (wt), about 10%DPEPA(wt), about 41% BisGMA (wt), about 0.25% CQ (wt); and a relativelyhydrophobic liner comprising about 29.5% BisGMA (wt), about 29.5% UDMA(wt), about 39% TriEDMA (wt), about 1.435% EDMAB (wt), and about 0.369CQ (wt), and 0.025 MEHQ (the “Sample”).

TABLE 5 LONG TERM AGING TEST OF ADHESIVES μ-TBS - EXPOSED SPECIMENS WITHDENTIN AS A SUBSTRATE (ALL RESULTS IN MPa) Total Etch Adhesives 24 HR(SD) 3 months 6 Months Sample in water 42.22 (13.53) 46.25 (13.32) 52.52(14.29) Sample + 48.41(7.53)  47.65 (6.46)  46.62 (9.82)  hydrophobicresin in water

In yet another embodiment, a dental adhesive system according to atleast one of the above formulations further comprises the use ofchlorhexidine dissolved in ethanol or a comparable alcohol or othersolvent having a solubility parameter approximately similar thereto as awetting solution prior to bonding the prepared dentin surface. As it isknown that chlorhexidine is a matrix metalloproteinase (“MMP”)inhibitor, and studies have indicated that endogenous MMP's maycontribute to collagen degradation and weakening adhesive bond strength,the below Table 6 shows the results of testing used to determine whetheruse of chlorhexidine interferes with a dental adhesive system accordingto at least one of the above formulations.

Four solutions were prepared: a control solution of water; a 1%chlorhexidine diacetate in water solution (CHX/Water); ethanol only(Ethanol); and 1% chlorhexidine diacetate in ethanol (CHX/Ethanol). Flatdentin surfaces were etched with 32% phosphoric acid, Uni-etch BAC(Bisco Inc.) during 15 s, rinsed thoroughly with water (30 s), and driedwith absorbent paper. Any visible water was remaining on the dentinsurface was removed and surfaces were re-wetted during 30 seconds withone of the solutions prepared, including the control groups (water andethanol without chlorhexidine). The excess of the solution was removedwith tissue-paper and an adhesive according to one of the embodimentsdiscussed above (Sample components A and B of Table 5 above), wasapplied with smooth and continuous rubbing during 15 seconds and leftundisturbed for 15 seconds. A gentle air stream was applied to evaporatethe solvents, and subsequently it was light-cured for 20 s (500 mW/cm²).Four-mm resin build-ups were constructed incrementally, using AeliteAll-purpose Body (Bisco). After storage in water at 37° C. for 24 h,teeth were cut into beams for microtensile test (0.5 mm/min). Half ofthe beams were tested immediately (24 h) and the other half was storedin distilled water, which was changed every month for 6 months. When thestorage period was completed, the remaining beams were tested. Data wereanalyzed by two-way ANOVA and Tukey for pairwise comparisons (α=0.05) toevaluate effects of treatments and testing periods. The tests below showthat there were no significant negative effects of treating the dentinwith any of the chlorhexidine solutions prior to bonding, either ininitial bond strength or at the 6 month period. It is believed that longterm bond strength may be improved due to the MMP inhibitive effects ofchlorhexidine, as well as the anti-microbial effects of chlorhexidine.Further, according to another embodiment, chlorhexidine dissolved inethanol is utilized as a portion of Part A or Part B of the adhesivesystems disclosed above.

TABLE 6 BOND STRENGTH AS A FUNCTION OF STORAGE TIME OF ADHESIVES μ-TBS -CHLORHEXIDINE (“CHX”) INFUSED SAMPLES WITH DENTIN AS A SUBSTRATE (ALLRESULTS IN MPa) Solution Used to Treat Prepared Dentin 24 HOURS 6 MONTHSWATER 49.41 ± 10.75 (19) 58.68 ± 8.95 (23) CHX + WATER 51.27 ± 17.28(16) 55.13 ± 15.87 (16) ETHANOL 58.27 ± 10.42 (20) 57.31 ± 10.11 (21)CHX + ETHANOL 53.08 ± 15.80 (21) 59.71 ± 12.92 (19)

What is claimed is:
 1. A polymerizable dental adhesive system foradhering dental restorations to dentin, enamel, and other dentalsurfaces comprising a first primer component comprising NTG-GMA, NPG, orother amino acids and their metal salts and a second primer componentcomprising BPDM, PMDM, or other polymerizable acidic monomers that donot interfere with polymerization of the primer system, the systemcomprising: a. including in the second primer component: (i) arelatively hydrophilic monomer in an amount that renders the systemrelatively hydrophilic before polymerization of the system and capableof penetrating a prepared dental surface such as etched tooth dentin orenamel, and a multi-functional cross-linking agent in amounts thatrenders the system relatively hydrophobic after polymerization; and (ii)a relatively hydrophobic polymerizable monomer that is relativelyhydrophobic after polymerization of the system; b. wherein the inclusionof said hydrophobic polymerizable monomer and said multi-functionalcross-linking agent improves the long term stability or durability ofthe polymerized primer system to the dental restoration and to thetooth, dentin, enamel and other dental surfaces.
 2. A dental adhesivesystem comprising: a. a first portion and a second portion operable tobe mixed prior to application to a dental surface, wherein (i) the firstportion comprises ethanol and N(p-tolyl) glycine glycidyl methacrylatemagnesium salt; (ii) the second portion comprises biphenyldimethacrylate (BPDM), 2-hydroxyethyl-methacrylate (HEMA), Bis-phenolglycidlymethacrylate (BisGMA), dipentaerythritol pentaacrylate (DEPA)and a light cure initiator system; and (iii) wherein the resultantadhesive system comprises a hybrid layer when applied to dentin that hasbeen treated with an acidic solution.
 3. The dental adhesive system ofclaim 2, wherein the resultant adhesive system does not show asignificant reduction in bond strength when exposed to an aqueoussolution.
 4. The dental adhesive system of claim 2, wherein theresultant adhesive system does not show a significant reduction in bondstrength when exposed to an aqueous solution for more than one month. 5.The dental adhesive system of claim 2, wherein the resultant adhesivesystem does not show a significant reduction in bond strength whenexposed to an aqueous solution for more than twenty-four months.
 6. Thedental adhesive system of claim 2, wherein the resultant adhesive systemdoes not show a significant reduction in bond strength when exposed toan aqueous solution for forty-five months or less.
 7. The dentaladhesive system of claim 2, further comprising a resin operable to beplaced over a cured or partially cured mixture of the first portion andthe second portion, and wherein the resin is without a hydrophilicmonomer.
 8. The dental adhesive system of claim 7, wherein thehydrophilic monomer is 2-hydroxyethyl methacrylate (HEMA).
 9. The dentaladhesive system of claim 2, further comprising a multifunctionalcross-linking agent.
 10. The dental adhesive system of claim 9, whereinthe multifunctional cross-linking agent is a polymerizable monomerhaving four or more (meth)acrylate groups.
 11. The dental adhesivesystem of claim 9, wherein the multifunctional polymerizable monomer isselected from the group comprising pentaacrylate and hexacrylate.
 12. Adental adhesive system showing improved stability and durabilityhydrolytic degradation of bonds, the adhesive system comprising: a. aprimer adhesive portion formed by the mixture of a part A comprisingethanol and N(p-tolyl) glycine glycidyl methacrylate magnesium salt witha part B comprising a hydrophilic resin comprising biphenyldimethacrylate (BPDM), 2-hydroxyethyl-methacrylate (HEMA), Bis-phenolglycidlymethacrylate (BisGMA), dipentaerythritol pentaacrylate (DPEPA),and a light cure initiator system; and b. a hydrophobic resin.
 13. Thedental adhesive system of claim 12, wherein the hydrophobic resinfurther comprises a filler.
 14. The dental adhesive system of claim 13,wherein the filler comprises approximately 10%-50% by weight of theadhesive system.
 15. The dental adhesive system of claim 14, wherein thehydrophilic Part B comprises approximately 10% BPDM, about 38.75% HEMA,about 10% DPEPA, about 41% BisGMA, about 0.25% CQ, and about 10%dipentaerythritol pentaacrylate.
 16. The dental adhesive system of claim14, further comprising use of a hydrophobic resin comprisingapproximately 25% BisGMA, approximately 25% urethane dimethacrylate(UDMA), approximately 47.77% triethyleneglycol dimethacrylate(Tri-EDMA), approximately 1.75% ethyl 4-dimethylaminobenzoate (EDMAB),approximately 0.45% camphorquinone CQ, and approximately 0.001%4-methoxyphenol (MEHQ).
 17. A polymerizable dental adhesive system foradhering dental restorations to dentin, enamel, and other dentalsurfaces comprising a first primer component comprising a magnesium saltof NTG-GMA, or other amino acids and their metal salts and a secondprimer component comprising BPDM, PMDM, or other polymerizable acidicmonomers that do not interfere with polymerization of the primer system,the system comprising: a. a first portion formed by the mixture of arelatively hydrophilic part comprising approximately 10% biphenyldimethacrylate (BPDM), about 38.75% 2-hydroxyethyl-methacrylate (HEMA),about 10% dipentaerythritol pentaacrylate (DPEPA), about 41% Bis-phenolglycidlymethacrylate (BisGMA), about 0.25% of a light cure initiatorsystem, and about 10% dipentaerythritol pentaacrylate; b. a relativelyhydrophobic resin comprising 25% Bis-phenol glycidlymethacrylate(BisGMA), approximately 25% urethane dimethacrylate (UDMA),approximately 47.77% triethyleneglycol dimethacrylate (Tri-EDMA),approximately 1.75% ethyl 4-dimethylaminobenzoate (EDMAB), approximately0.45% of a light cure initiator system and optionally approximately0.001% 4-methoxyphenol (MEHQ).